1. Field of the Invention
The present invention generally relates to a liquid crystal display (LCD), and more particularly, to an LCD having good color reproducibility.
2. Description of Related Art
Since an LCD has advantages, such as small size, high display quality, low power consumption and no radiation, the LCD has played a major role in the mainstream display market overwhelming the traditional cathode ray tube (CRT) display. However, in comparison with the CRT display, an LCD requires a backlight source to display images. The common backlight source of an LCD includes cold-cathode fluorescent lamp (CCFL), clod-cathode flat fluorescent lamp (CCFFL) or light-emitting diodes (LEDs).
A white LED has advantages, such as low heat dissipation, power-saving, long lifetime, fast response speed, small size and surface mount feasibility; therefore, the white LED has been viewed as ‘a white lighting revolution’. In the market of various applications, the white LED has been gradually applied to a backlight module of a handheld display or a portable display due to the advantages of power-saving, small size and fast response speed. However, a common white LED is usually implemented by using a blue LED chip in association with an YAG (yttrium aluminum garnet) phosphor because the white LED including the blue LED chip and YAG phosphor has the advantages of packaging convenience and small size, but the color saturation of the white LED is still not good enough. In particular, in contrast with a CCFL backlight module, the backlight module having white LEDs more likely brings a color-shift phenomenon, for example, an orange-shift problem usually occurs with an LCD.
FIG. 1A is a green chromaticity coordinate diagram of a conventional LCD. Referring to FIG. 1A, the green chromaticity coordinate points of a conventional LCD during displaying green color mostly fall out of a region 10 in FIG. 1A, which causes a yellow-shift greenish color to be displayed. In other words, in order to normally display green color by an LCD, the green chromaticity coordinate points must fall within the region 10 of FIG. 1A. However, limited by the nature of white LEDs (having an architecture of a blue LED chip in association with YAG phosphor), a color-shift phenomenon usually occurs in a conventional LED during displaying green color.
FIG. 1B is a color space chromaticity coordinate diagram according to CIE 1931 chromaticity coordinate diagram. Referring to FIG. 1B, the red chromaticity coordinate points of a conventional LED mostly fall within a region 11 in FIG. 1B, which causes an orange-shift redish color to be displayed during displaying red color. Similarly, limited by the nature of white LEDs (having an architecture of a blue LED chip in association with YAG phosphor), a color-shift phenomenon usually occurs in a conventional LED during displaying red color.
It can be seen from the prior art that when an LCD employing a backlight module of white LEDs is displaying color images, the green color and the red color are displayed with color-shift, which degrades the color saturation of the LCD.